Thu gọn biểu thức sau a) A = ( a+ b – c + d ) – ( - a – b + c – d ); b) B= ( a+ b –c )
Giải thích
a) A = ( a+ b – c + d ) – ( - a – b + c – d )
= a+ b – c + d + a + b - c + d
= 2a + 2b + 2d – 2c
b) B = ( a+ b – c ) + ( a – b ) – ( a – b - c )
= a+ b – c + a – b – a + b + c
= a + b